The subject matter disclosed herein relates to non-invasive imaging and, in particular, to spectral calibration of a radiographic imaging system.
In the fields of medical imaging and security screening, non-invasive imaging techniques have gained importance due to benefits that include convenience, and speed. In medical and research contexts, non-invasive imaging techniques are used to image organs or tissues beneath the surface of the skin. Similarly, in industrial or quality control (QC) contexts, non-invasive imaging techniques are used to examine parts or items for hidden defects that may not be evident from an external examination. In security screening, non-invasive imaging techniques are typically used to examine contents of containers (e.g., packages, bags, or luggage) without opening the containers and/or to screen individuals entering or leaving a secure location.
One example of a non-invasive imaging system is a computed tomography (CT) imaging system in which an X-ray source emits radiation (e.g., X-rays) towards an object or subject (e.g., a patient, a manufactured part, a package, or a piece of baggage) from a variety of different angular positions. The emitted X-rays, after being attenuated by the subject or object, typically impinge upon an array of radiation detector elements of an electronic detector, which generates signals indicative of the incident radiation at different locations on the detector. A gantry containing the X-ray source and radiation detectors may be rotated about the object, or the object may be rotated while the positions of X-ray source and radiation detectors are held fixed. The intensity of radiation reaching the detector is typically dependent on the X-ray spectrum emitted from the X-ray tube and the attenuation and absorption of X-rays through the scanned subject or object. The signals generated at the detector are processed to generate images and/or volumetric representations of the internal structures of the subject or object.